Wireless charging technology is widely used in devices such as mobile devices, electric cars, home appliances, etc. In radio frequency (RF) charging, a transmitter wirelessly transmits a radio wave, which is received by a receiver wirelessly to generate electrical energy. The RF charging has several traits that contribute to its popularity, gradually becoming the mainstream wireless charging technology: multiple receivers can receive the radio wave simultaneously, and a distance between each receiver and the transmitter can be greater than 4.5 meters.
First, a conventional receiver stores the electrical energy generated from the radio wave in an energy storage element (e.g., a lithium battery), and then outputs the electrical energy released from the energy storage element to an energy consuming device. Since the conventional receiver always performs electrical energy transfer twice on the electrical energy generated from the radio wave, it has relatively high electrical energy loss and thus relatively low energy usage efficiency.